Impact of high-intensity exercise on energy expenditure, lipid oxidation and body fatness.

OBJECTIVE: Two studies were conducted to assess the potential of an increase in exercise intensity to alter energy and lipid metabolism and body fatness under conditions mimicking real life. METHODS: Study 1 was based on the comparison of adiposity markers obtained in 352 male healthy adults who participated in the Québec Family Study who either regularly participated in high-intensity physical activities or did not. Study 2 was designed to determine the effects of high-intensity exercise on post-exercise post-prandial energy and lipid metabolism as well as the contribution of beta-adrenergic stimulation to such differences under a real-life setting. RESULTS: Results from Study 1 showed that men who regularly take part in intense physical activities display lower fat percentage and subcutaneous adiposity than men who never perform such activities, and this was true even if the latter group reported a lower energy intake (917 kJ/day, P<0.05). In Study 2, the high-intensity exercise stimulus produced a greater post-exercise post-prandial oxygen consumption as well as fat oxidation than the resting session, an effect which disappeared with the addition of propranolol. In addition, the increase in post-prandial oxygen consumption observed after the high-intensity exercise session was also significantly greater than that promoted by the low-intensity exercise session. CONCLUSION: These results suggest that high-intensity exercise favors a lesser body fat deposition which might be related to an increase in post-exercise energy metabolism that is mediated by beta-adrenergic stimulation.

A possible role for palatability of the food in diet-induced thermogenesis.

OBJECTIVE: A regulatory increase in energy expenditure, induced by excess intake of palatable food (cafeteria diet), is well documented. It has also been shown that excess feeding by gastric intubation, fails to enhance thermogenesis, suggesting that the palatability of the food could have a role in producing this regulatory response. A study was planned to find out if a palatable diet pair-fed with standard laboratory chow would produce diet-induced thermogenesis (DIT) and if the brown adipose tissue (BAT) was involved in this process. DESIGN: Body weight gain, BAT activity and body temperature response to norepinephrine were measured in rats fed for 40 d either the standard laboratory pellets (control), a palatable high carbohydrate diet fed ad libitum and the same palatable diet but fed in restricted amounts to match the intake of the control group. RESULTS: It was found that palatable food either fed ad libitum or pair-fed, increased DIT and reduced food efficiency (which is the body weight gain per 100 kj of food consumed). These responses were paralleled by increased BAT activity and enhanced response to noradrenaline. Since the DIT with pair-feeding was proportionally as large as with excess intake of the same food in the group fed ad libitum, it is concluded that the palatability of the food, rather than the excess intake per se, is responsible for the increased thermogenesis. CONCLUSIONS: DIT was observed when palatable food was fed either ad libitum or in restricted amounts. It is suggested that the palatability of the diet rather than the quantity or composition of the ingested food is responsible for the DIT. It is also proposed that the excess energy expenditure due to sensory stimulation induced by palatable food, is directly related to an enhanced sympathetic activity which stimulates the BAT thermogenic capacity.

Tissue specificity of SNS response to exercise in mice exposed to low temperatures.

The present study was carried out to investigate the tissue specificity of the sympathetic nervous system (SNS) response to acute exercise in adult mice exposed to four ambient temperatures. SNS activity estimates in heart, pancreas, and brown adipose tissue (BAT) were obtained from the measurement of the dopamine (DA) tissue contents 1 h after the inhibition of the DA-beta-hydroxylase with 1-cyclohexyl-2-mercaptoimidazole (CHMI). DA was measured by electrochemical detection after the separation of the monoamine using high-performance liquid chromatography. In both heart and pancreas, temperature and activity influenced DA tissue contents after the CHMI injection. In these tissues, and regardless of whether mice were resting or exercising, the DA contents gradually increased while the ambient temperature was dropped from a thermoneutral temperature of 32 to 5 degrees C. In BAT, however, there was a significant interaction between temperature and activity on the tissue DA content; in contrast to what was observed in resting animals, DA did not uniformly augment in exercising mice when the temperature was decreased from 32 to 5 degrees C. In summary, the present results show that exercise can attenuate the stimulating effect of cold on SNS activity in BAT. This effect is seemingly specific to BAT because, in mice exposed to low ambient temperatures, SNS activity in both heart and pancreas is not lower in exercising than in resting animals.

A rare tumor at the elbow: a glomangioma. Differential diagnosis and therapy.

Referring to a case of a glomangioma at the elbow, several aspects of this tumor are illustrated. Since the related hemangiopericytoma can be distinguished from the glomangioma by its biological behavior, the morphological differential diagnosis of both tumors is discussed in detail. Therapeutic consequences of one or the other diagnosis are also indicated.

Diagnosis and therapy for a leiomyosarcoma of vascular origin.

A case of a leiomyosarcoma of vascular origin in the left calf is presented. Because of the rarity of occurrence, some clinical aspects, and in particular, diagnostic procedures and therapy for the tumor, are discussed along with a review of recent literature.

Subpicosecond time-resolved vibrational spectroscopy by transient infrared absorption.

A technique to record transient vibrational spectra with 0.5-psec resolution is reported. The apparatus is based on seeded optical parametric amplification. A study of the microscopic details of the photodissociation of carboxyhemoglobin is described as an example.

Enhanced metabolic response to caffeine in exercise-trained human subjects.

The effect of caffeine on resting metabolic rate (RMR) was investigated in eight trained and eight nontrained young male subjects. The ingestion of 4 mg/kg caffeine produced a greater increase of RMR in trained subjects. This effect was associated with a greater increase in plasma free fatty acids and a larger fall in respiratory quotient, indicating an enhanced lipid oxidation following caffeine in exercise-trained subjects. An initial fall in plasma glucose was observed but only in trained subjects, and caffeine did not change plasma insulin in either group studied. Caffeine caused a significant fall in plasma norepinephrine and an increase in plasma epinephrine in both groups of subjects, but this action was significantly greater in trained subjects. It is suggested that the greater increase in RMR observed in trained subjects following caffeine ingestion is related to an enhanced lipid mobilization, possibly produced by a greater epinephrine secretion and by subsequent increased lipid oxidation.

Hormonal factors in reduced postprandial heat production of exercise-trained subjects.

The influence of exercise training on postprandial heat production was investigated in human subjects. Whereas resting metabolic rate was comparable for trained and nontrained subjects, the heat increment of feeding (HIF) after subjects consumed a meal containing 755 kcal was approximately 50% smaller in the trained subjects. Measurements of respiratory quotient also indicated a reduction of about 50% in glucose oxidation associated with exercise training. The levels of plasma norepinephrine increased significantly (P less than 0.01) from 200 to 300 pg/ml in the sedentary subjects, but the changes observed in trained subjects were not significant. During the early phase of the meal, plasma levels of insulin were increased, even before nutrients appeared in the blood. Throughout the study the enhanced sensitivity to insulin of the trained subjects was confirmed. the postprandial heat production was diminished in exercise-trained subjects, and it is suggested that this could be related to a reduced activity of the sympathetic nervous system. Another possibility is that this reduction in HIF is related to a facilitation of glucose disposal in the form of glycogen rather than in the form of lipids.

Familial resemblance in catecholamine changes to cold stress and maximal exercise.

Parents and children from 38 families were submitted to a cold-stress and maximal treadmill test. The number of subjects varied depending on the measurements. Plasma epinephrine and norepinephrine, blood pressure and heart rate were measured before, during and after a cold hand immersion test (in a water bath at 5 degrees C for 2 min), as well as before and after maximal exercise (modified Balke). Scores were adjusted for the effects of age and sex through multiple-regression procedures (age + sex + age X sex + age2 + age3), yielding residuals which were submitted to analysis. Characteristic variations during cold stress were observed. Maximal exercise yielded a mean aerobic power of 43 ml/kg min-1 (SD = 10), a mean maximal heart rate of 192 (SD = 10) and a mean maximal blood lactate of 65 mg/100 ml (SD = 23). Family resemblances in cold stress and maximal exercise adaptive reactions were investigated by comparison of between-family over within-family means of squares. In response to the cold stress, there were indications of family lines in induced changes for systolic blood pressure, epinephrine, and total catecholamines at 1 min after the test (p less than or equal to 0.05). Furthermore, parent-child correlations were significant and reached 0.38 for epinephrine, 0.28 for norepinephrine, and 0.34 for total catecholamines. Familial concentrations could not be detected before or 8 min after the cold stress. There are no indications of family resemblance in plasma catecholamine concentrations following exposure to maximal-exercise stress. It is concluded that genetic variation is probably contributing only moderately to catecholamine changes under cold stress and very little under exercise stress.

Role of exercise-training in the prevention of hyperinsulinemia caused by high energy diet.

The present study was undertaken to determine whether exercise-training done in combination with feeding a high energy diet could modulate carbohydrate metabolism. Male rats were divided into exercise-trained or sedentary groups that received either a palatable high energy diet or merely standard laboratory diet. After 10 weeks of training, the animals were subjected to an intravenous glucose tolerance test. Body weight, epididymal fat pads, and adipocyte volume were reduced following training. The results also showed that exercise-training protects against deterioration of glucose tolerance produced by high energy diet. Training prevented the elevation of basal as well as glucose challenged insulin levels induced by the high energy diet in spite of a high fat as well as high overall energy intake. A highly significant coefficient of correlation (r = 0.78, P less than 0.01) was observed between the size of adipocytes and the insulin response to glucose load and suggests that the prevention of hyperinsulinemia in rats fed high energy foods while training could be associated with the ability to prevent obesity.

Catecholamines and triiodothyronine variations and the calorigenic response to norepinephrine in cold-adapted and exercise-trained rats.

A comparison was made of the thermogenic response to norepinephrine (NE) in cold-adapted (2 h per day at -15 degrees C for 5 weeks) and in exercise-trained rats (2 h swimming per day for 5 weeks). The oxygen consumption and the plasma catecholamine elevation were comparable for both conditions. Similarly plasma corticosterone determinations indicated comparable elevations in acute stress exposure and reduced responses in both exercise-trained and cold-adapted rats. The marked increase in colonic temperature which was observed in cold-adapted animals injected with NE (30 micrograms/100 g s.c.) was not found in exercise-trained rats. Similarly the brown adipose tissue was double in size in the cold-adapted rats but remained unchanged with exercise training. An important elevation of triiodothyronine (T3) was found in cold-exposed rats, either adapted or not. However, exercise was found to decrease plasma T3 in trained and nontrained rats. The results indicate that swimming for 2 h and exposure to cold (-15 degrees C) for 2 h produced comparable elevation of plasma corticosterone and catecholamine, and of oxygen consumption. However, only the cold-adapted animals develop a NE-induced thermogenesis. It is suggested that thyroid hormones are necessary as permissive factor, in stress-induced thermogenesis.

Interactions between dietary obesity and exercise-training on carbohydrate metabolism.

The present study addressed the important question of whether exercise-training could reduce insulin levels in exercise-trained rats made obese by a diet composed of palatable foods. Female rats were divided in exercise-trained or in sedentary groups which receive either a palatable high-energy diet or merely a standard laboratory chow. The high-energy diet was composed of supermarket foods including chocolate chips cookies, pop-corn, bologna, etc. Exercise-training program consisted of forced swimming, 6 d per week, 2 h per d, in water maintained at 36 degrees C. At the end of both fattening and exercise-training program, the animals were subjected to an intravenous glucose tolerance test. The results showed that high-energy diet and exercise-training had opposite effects on both glucose tolerance and insulin secretion: the former impaired glucose tolerance and increased insulin levels, whereas the latter leads to opposite adaptations. In addition, some abnormalities in insulin metabolism persisted in rats simultaneously assigned to exercise-training and high-energy diet. Thus, the present results also suggested that physical training alone could not reduce plasma insulin under control levels, and that a change in energy balance is possibly necessary to achieve this purpose.

Glycogen and nonspecific adaptation to cold.

Exposure to moderate cold for a few weeks causes adaptation through the development of nonshivering thermogenesis primarily in the brown adipose tissue. Exposure to severe cold by repeated short exposures also causes adaptation but by mechanisms that seem to be different. These latter results were confirmed in mice. It was also found that this type of adaptation is nonspecific because it can be produced by other stresses such as swimming or fasting. Simultaneous determinations of glycogen in the liver and soleus and tibialis muscles indicated a possible role for this substrate in cold resistance. Repeated cold exposure (8 times at -15 degrees C for 10 min), swimming for 3 h, or fasting for 48 h--all reduced the glycogen stores when measured immediately after the stress. However, the levels of glycogen were significantly increased above the initial values (P less than 0.01) when the determinations were made 24 h later. Cold tolerance measured by resistance to hypothermia at -5 degrees C was improved only when the test was done 24 h after the stress had taken place. Thus, cold resistance, as described in this study, is nonspecific and our results suggest that glycogen stores could serve as a rate-limiting substrate.

Plasma catecholamines and cardiovascular responses to cold and mental activity.

Plasma epinephrine (E) and norepinephrine (NE) as well as blood pressure and heart rate variations were measured in 12 male subjects before, during, and after a cold hand test (5 degrees C for 2 min), a mental arithmetic test, and a combination of both these tests. Although the cold and mental tests had comparable effects on blood pressure, the heart rate response was greater than the mental test. The mental test produced a greater increase of E than the cold test, but the effect of the cold test was greater on NE than on E. Changes in heart rate were significantly correlated with E variations but not with NE, whereas changes in blood pressure were correlated with NE. Resting NE was correlated with resting blood pressure and resting E with resting heart rate. Finally the levels of basal E were positively correlated with the increase in E during the test. Cardiovascular changes were shown to be differently modified by a mental and a cold test. Evidence was given indicating that these changes are related to differences in E and NE responses in the presence of these tests.

Metabolic and cardiovascular responses to norepinephrine in trained and nontrained human subjects.

Forty young male adults, aged 18-30 yr, with maximal oxygen intake (VO2 max) varying between 35 and 76 ml-kg-1-min-1 were studied. The fasting subjects were perfused for 15 min with saline and thereafter for 30 min with norepinephrine (0.1 mug/kg per min). Blood variables were determined at the end of slaine perfusion, at 15 and 30 min during norepinephrine perfusion and 15 min after the end of NE perfusion. Trained subjects are characterized by lower basal plasma glucose and insulin concentration. NE perfusion produced a larger increase in plasma glucose in the trained subjects. Levels of insulin in the postperfusion period were smaller in the trained group. Serum free fatty acids (FFA) and glycerol increased less in the trained subjects during NE perfusion and this difference persisted in the post-perfusion period. During NE perfusion, blood lactate increased only in the nontrained subjects. Initial heart rate and blood pressure were lower in trained subjects but, during NE perfusion, elevated levels of blood pressure and decreased levels of heart rate were comparable in both groups. Because of similarities in responses to exercise and to NE in trained subjects, the results of the present study suggest a possible role for NE in exercise training.